use of inner type within custom deserialization logic stack overflows at compilation

[Dowwie]

This is a problem where something that worked fine for a very long time no longer works: the use of an inner Deserializable type within custom Deserialization logic

https://play.integer32.com/?version=stable&mode=debug&edition=2018&gist=0d5d637f9cc699a1e1d22d020541f934

I've used the InnerSettings type (L19) with success for a long time and only now is it stack overflowing at compile time. Moving InnerSettings out of the custom deserialization logic solves the issue. Therefore, it seems that something changed in a recent version of serde/derive. Would someone please confirm?

Additionally, I've tried this on macos laptop and it compiles w/rustc 1.36 stable. It fails to compile on debian and on the playground.

If you were to run these as a package: https://gist.github.com/Dowwie/3483499835880f7f943d911e6354be0d

Thanks!

-Darin

[dtolnay]

This is a compiler bug, not something that changed in serde -- rust-lang/rust#55779. As a workaround it should work if you put extern crate serde in the crate root.

[Dowwie]

@dtolnay correct! that worked. thank you!